Fix the reported shader gl_MaxDrawBuffers to be compliant with the new EXT_draw_buffers spec. From the extension spec: "8) What value should gl_MaxDrawBuffers in the shading language report?" "RESOLVE: It should match MAX_DRAW_BUFFERS_EXT from the API. None of the API or GLSL specifications explicitly state the linkage between API and SL constants, but it seems logical that one would expect them to match, regardless of whether or not an extension directive is used in the shading language." TRAC #23509 Signed-off-by: Shannon Woods Signed-off-by: Nicolas Capens Authored-by: Jamie Madill